Lithium secondary battery including water-dispersible binder, conduction agent, and fluoroethylenecarbonate

ABSTRACT

The present invention relates to a lithium secondary battery. The present invention provides the lithium secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution. The negative electrode includes a water-dispersible binder and a conduction agent. The non-aqueous electrolyte solution includes fluoroethylenecarbonate (FEC). The batteries of the present invention are advantageous in that they have a high efficiency charging lifespan characteristic and enable high capacity charging in a short time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. patent applicationSer. No. 12/909,267 filed on Oct. 21, 2010, which is a Continuation ofPCT International Application No. PCT/KR2010/004688 filed on Jul. 19,2010, which claims the benefit of Patent Application No. 10-2009-0065418filed in Republic of Korea, on Jul. 17, 2009. The entire contents of allof the above applications is hereby incorporated by reference into thepresent application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lithium secondary battery having ahigh efficiency charging lifespan characteristic and enabling highcapacity charging in a short time and, more particularly, to a lithiumsecondary battery including a water-dispersible binder, a conductionagent, and fluoroethylenecarbonate.

2. Discussion of the Related Art

Today, commercial electrode binders chiefly used to fabricate secondarybatteries include polyvinyllidene fluoride (hereinafter referred to as‘PVDF’)-based polymers, PVDF homopolymers, polyvinylidene fluoridehexafluoropropylene copolymers (Korean Patent Application PublicationNo. 2001-0055968), and polyvinyllidene fluoride-chlorotrifluoroethylenecopolymers.

The PVDF-based polymers are advantageous that they are stable chemicallyand electrochemically, but may have environmental problems resultingfrom organic solvents, such as NMP (N-methyl-2-pyrrolidone), becausethey have to be dissolved in the organic solvents and used as bindercompositions.

Further, the PVDF-based polymers are dangerous because of a low safetyand become the root cause of a reduction in the performance ofelectrodes due to a low affinity with a liquid electrolyte.

In addition, the PVDF-based polymers are excellent in the bindingcharacteristic with inorganic substance particles, such as activematerials, because they act with it surrounding the circumference of theactive materials, but are disadvantageous it that they must be used in alarge quantity in order to exhibit and maintain sufficient adhesivestrength because they have poor adhesive strength with a currentcollector such as metal.

In order to solve the above problems, a water-dispersible electrodecomposition using water as a dispersion medium (i.e., a solvent) wasproposed. In this case, a water-dispersible binder is used instead ofthe above-described PVDF-based binder. Styrenebutadiene rubber (SBR) ischiefly used as the water-dispersible binder. In an electrode using thewater-dispersible binder, a binding effect is higher than that of anon-aqueous (i.e., an organic solvent-based) binder although thewater-dispersible binder is used in a small quantity and thus the ratioof presence of active materials per the same volume can be increased,thereby being capable of achieving a high capacity and a long lifespancharacteristic. Accordingly, it is expected that batteries adoptingnegative electrodes using the water-dispersible binder will become themain stream in the future.

For a conventional process of fabricating the negative electrodes of asecondary battery using water as a dispersion medium, reference can bemade to a document 1 below. The document 1 discloses influence ofcarboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) on thestability of suspensions in a process of fabricating water-basedsuspensions of natural graphite which is a material for a lithium ionbattery negative electrode; electrokinetic behavior and flexiblebehavior in order to evaluate the dispersion stability of suspensionsaccording to organic additives; a shaping micro structure and a poreratio of as-castsheet and correlation therebetween, etc.

[Document 1] Jin-Hyon Lee, ┌Process of fabricating water-basedsuspensions of materials for negative electrodes of lithium ionbatteries and evaluation of battery characteristics┘, a thesis for amaster's degree, Hanyang University, 2005.

SUMMARY OF THE INVENTION

As described above, in order to solve the conventional problemsconcerned with the negative electrode fabricated using a non-aqueoussolvent, a technique in which a negative electrode is fabricated using awater-dispersible solvent was proposed, but no problem does not exist inthe technique.

The negative electrode using water as a solvent of an electrode slurryand also using a water-dispersible binder is advantageous in that anadditional conduction agent needs not to be used in the electrodebecause of an excellent conduction characteristic, but is problematic inthat if several conditions are not optimized in a process of drying theelectrode, the electrical conductivity of the electrode is reduced.

Further, the conventional negative electrode using a water-dispersiblebinder is also problematic in that satisfactory performance is not meteven in a high efficiency charging lifespan characteristic and a highcapacity charging speed per unit time.

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a battery which is capable of improving thecharacteristics of a negative electrode by adding a conduction agent toa water-based negative electrode and of improving a high efficiencycharging lifespan characteristic and enabling high capacity charging ina short time by using specific additives in an electrolyte.

The present invention has been made to solve the conventional problemsand provides a lithium secondary battery including a positive electrode,a negative electrode, and a non-aqueous electrolyte solution, whereinthe negative electrode comprises a water-dispersible binder and aconduction agent, and the non-aqueous electrolyte solution comprisesfluoroethylenecarbonate (FEC).

Further, the present invention provides the lithium secondary battery inwhich the fluoroethylenecarbonate (FEC) is included in an amount of 10to 15 wt % based on a total amount of the non-aqueous electrolytesolution including the fluoroethylenecarbonate (FEC).

Further, the present invention provides the lithium secondary battery inwhich ethylenecarbonate (EC) is included in an amount of 85 to 90 wt %based on a total amount of the non-aqueous electrolyte solutionincluding the ethylenecarbonate (EC).

Further, the present invention provides the lithium secondary battery inwhich the conduction agent is one or a combination of two or moreselected from acetylene black, carbon black, and graphite.

Further, the present invention provides the lithium secondary battery inwhich the conduction agent is included in an amount of 0.2 to 0.8 wt %.

Further, the present invention provides the lithium secondary battery inwhich the water-dispersible binder is one or a combination of two ormore selected from styrene-butadiene rubber, acrylonitrile-butadienerubber, acrylonitrile-butadiene-styrene rubber, carboxymethyl cellulose,and hydroxypropylmethyl cellulose.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of some embodiments givenin conjunction with the accompanying drawing, in which:

FIG. 1 is a graph showing cycle characteristics according to anembodiment of the present invention and a comparison example.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, some embodiments of the present invention will be describedin detail.

In the present invention, in a lithium secondary battery, including apositive electrode, a negative electrode, and a non-aqueous electrolytesolution, the negative electrode includes a water-dispersible binder anda conduction agent, and the non-aqueous electrolyte solution includesfluoroethylenecarbonate (FEC).

In the present invention, the negative electrode includes thewater-dispersible binder.

In general, a negative electrode is fabricated by forming a negativeelectrode-forming mixture in which negative electrode active materials,a binder, etc. and a solvent are uniformly mixed in an appropriateratio, coating the negative electrode-forming mixture on a currentcollector, and drying and compressing the result. Here, a non-aqueoussolvent is chiefly used as the solvent. This is because the non-aqueoussolvent is advantageous in terms of a guaranteed binding capacitybetween active materials.

However, the organic solvent in itself can not only lead toenvironmental problems, but become a fundamental cause of a reduction inthe performance of an electrode because of a low affinity with a liquidelectrolyte.

Accordingly, in the negative electrode of the present invention, unlikethe prior art, substance fabricated using water is used as the solvent.In this case, substance widely used in a non-aqueous solvent cannot beused but only the water-dispersible binder must be used as the binderincluded to bind the negative electrode active materials together.

In the present invention, conventional water-dispersible binders widelyused can be unlimitedly used as the water-dispersible binder. One or acombination of two or more, selected from styrenebutadiene rubber,acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber,carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose,polyvinylalcohol, hydroxypropyl cellulose, and diacetyl cellulose, canbe used as the water-dispersible binder. In particular, it is preferredthat a mixture in which styrenebutadiene rubber and carboxymethylcellulose are appropriately mixed be used as the negative electrodebinder.

It is preferred that the water-dispersible binder be used in an amountof 1 to 4 wt % based on the total amount of an electrode compositionincluding the water-dispersible binder. If the water-dispersible binderis used in an amount of less than 1 wt %, the adhesive strength ofactive materials is weakened, and so the active materials can be secededin a charging and discharging process. If the water-dispersible binderis used in an amount of more than 4 wt %, the amount of ac materials isreduced, which is not preferable in terms of the capacity of thebattery.

Further, in the present invention, the negative electrode includes theconduction agent.

In general, in the case in which a solvent used when a negativeelectrode is fabricated is water in the case of a water-dispersiblesolvent), an additional conduction agent is not used. This is because anegative electrode, fabricated using a water-dispersible solvent and awater-dispersible binder in itself, has an excellent conductioncharacteristic and so does not need to use an additional conductionagent.

However, the negative electrode using the water-dispersible solvent andthe water-dispersible binder is problematic in that the conductivity ofthe electrode is deteriorated in a dry environment. The inventor of thepresent invention has found that as charging characteristic (inparticular, a high efficiency charging characteristic) is improved evenin a dry environment if an appropriate amount of a conduction agent isused in the negative electrode using a water-dispersible solvent and awater-dispersible binder.

Accordingly, in the present invention, the conduction agent, togetherwith water-dispersible binder, is included in a negative electrode.

It is preferred that the conduction agent be included in an amount of0.2 to 0.8 wt %. If the conduction agent is included in an amount ofmore than 0.8 wt %, the amount of electrode active materials is reduced,which is not preferable in terms of the capacity of the battery.Further, it may not be preferable in maintaining the adhesive strengthof the electrode active materials because the amount of the binder isreduced as much as an increased amount of the conduction agent. If theconduction agent is included in an amount of less than 0.2 wt %, thereis a possibility that a high efficiency charging characteristic may notbe achieved because conductivity is less improved.

Common substance used to fabricate electrodes can be unlimitedly used asthe conduction agent. Examples of the common substance which can be usedas the conduction agent can include one or a combination of two or moreselected from acetylene black, carbon black, natural graphite,artificial graphite, Ketjen black, and carbon fiber. Further, a mixtureof conductive materials, such as polyphenylene derivatives, can be usedas the conduction agent.

The negative electrode included in the lithium secondary batteryaccording to the present invention can be obtained by coating a mixture,including the negative electrode active materials, the water-dispersiblebinder, and the conduction agent, on a current collector and then dryinga solvent (water).

The negative electrode active materials can include carbon and graphitematerials, such as natural graphite, artificial graphite, expandedgraphite, carbon fiber, non-graphitizing carbon, carbon black, carbonnanotubes, fullerenes, and activated carbon; metal, such as Al, Si, Sn,Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, or Ti which can be alloyed withlithium, and a compound containing the elements; a complex of metal anda compound thereof and carbon and graphite materials; and nitridescontaining lithium, but not limited thereto.

In particular, it is preferred that in order for the negative electrodeactive materials to be well sprayed in water (i.e., a solvent), theparticle diameter of the negative electrode active materials be a minesize. More particularly, it is preferred that the particle diameter ofthe negative electrode active materials be 5 to 30 μm.

The negative electrode mixture is a component prohibiting the expansionof a negative electrode and it can optionally include a filler. Thefiller is not specially limited so long as it is fibrous materials whichdo not cause a chemical change of a corresponding battery. For example,olefine-based polymers, such as polyethylene and polypropylene, andfibrous materials, such as glass fiber and carbon fiber, can be used asthe filler.

The fluoroethylenecarbonate (FEC) used in the non-aqueous electrolytesolution of the present invention is a component which is included inthe non-aqueous electrolyte solution as an additive.

The inventor of the present invention has found that when thefluoroethylenecarbonate (FEC) is included in the non-aqueous electrolytesolution a an additive, a secondary battery has a high efficiencylifespan characteristic and enables high capacity charging per unittime. It is estimated that a dielectric constant is high when thebattery is initially charged and an SEI film with excellent lithium ionconductivity can be formed because the fluoroethylenecarbonate (FEC)includes fluorine having a strong electron attraction effect. Actually,it was found that a charging characteristic per unit time and a cyclecharacteristic, of the battery, were improved when thefluoroethylenecarbonate (FEC) was included in the non-aqueouselectrolyte solution as an additive (for this, please refer to anembodiment to be described later).

It is preferred that the fluoroethylenecarbonate (FEC) be included in anamount of 10 to 15 wt % based on the total amount of the non-aqueouselectrolyte solution including the fluoroethylenecarbonate (FEC). If thefluoroethylenecarbonate (FEC) is included in an amount of less than 10wt %, fluoroethylenecarbonate is exhausted during a long-term cycle andthere is a possibility that the amount of fluoroethylenecarbonate may beinsufficient in the later part of the cycle.

If the fluoroethylenecarbonate (FEC) is included in an amount of morethan 15 wt %, there is a possibility that the cost of the battery canincrease because of the excessive use of expensivefluoroethylenecarbonate (FEC) and the performance of the battery can bedeteriorated when high efficiency discharging is performed because theresistance of a positive electrode is excessively increased.

Substance used to fabricate electrodes can be unlimitedly used as a basesolvent forming a constituent component of the non-aqueous electrolytesolution, together with the fluoroethylenecarbonate (FEC). The basesolvent can include one or more selected from the group comprisingpropylene carbonate (PC), ethylene carbonate (EC), diethylcarbonate(DEC), dimethylcarbonate (DMC), dipropylcarbonate (DPC),dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane,tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate(EMC), fluoroethylene carbonate (FEC), formic methyl, formic ethyl,formic propyl, methyl acetate, ethyl acetate, propyl acetate, pentylacetate, propionate methyl, propionate ethyl, propionate ethyl, andpropionate butyl. In an embodiment of the present invention,ethylenecarbonate (EC) of 85 to 90 wt % was used as the base solvent.

Further, the non-aqueous an electrolyte can further include otheradditives in order to improve a charging/discharging characteristic,flame retardant, etc. Examples of other additives can include pyridine,triethylphosphite, triethanolamine, cyclic ether, ethylene diamine,n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur,quinone imine dyes, N-substitution oxazolidinone, N,N-substitutionimidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole,2-methoxy ethanol, and trichloro aluminum. In some cases, a solventcontaining halogen, such as carbon tetrachloride or ethylenetrifluoride, can be further included in order to assignnoninflammability and dioxide carbonic gas may be further included inorder to improve a high-temperature preservation characteristic.

The remaining components of the lithium secondary battery according tothe present invention are described below.

The positive electrode can be fabricated by coating a mixture ofpositive electrode active materials, a conduction agent, and a binder ona positive electrode current collector and drying the result. In somecases, a filler may be further included in the mixture.

The positive electrode active materials can include a stratifiedcompound, such as lithium cobalt oxide (LiCoO₂) and lithium nickel oxide(LiNiO₂), or a compound in which one or more transition metals aresubstituted; lithium manganese oxides such as a Chemical FormulaLi_(1+x)Mn_(2−x)O₄ (where x is 0 to 0.33), LiMnO₃, LiMn₂O₃, and LiMnO₂;lithium copper oxides (Li₂CuO₂); vanadium oxides such as LiV₃O₈,LiFe₃O₄, V₂O₅, and Cu₂V₂O₇; Ni-site type lithium nickel oxidesrepresented by a Chemical Formula LiNi_(1−x)MxO₂ (where M=Co, Mn, Al,Cu, Fe, Mg, B, or Ga and x=0.01 to 0.3); lithium manganese complexoxides represented by a Chemical Formula LiMn_(2−x)M_(x)O₂ (where M=Co,Ni, Fe, Cr, Zn, or Ta and x=0.01 to 0.1) or Li₂Mn₃MO₈ (where M=Fe, Co,Ni, Cu, or Zn); LiMn₂O₄ in which sonic of Li of the above chemicalformula is substituted with alkaline-earth metal ions; a disulfidecompound; Fe₂(MoO₄)₃, and so on, but not limited thereto.

In general, the positive electrode current collector is made in athickness range of 3 to 500 μm. The positive electrode current collectoris not specially limited so long as it does not cause a chemical changein a corresponding battery and has high conductivity. For example,stainless steel, aluminum nickel, titanium, elementary carbon, oraluminum, or a current collector in which carbon, nickel, titanium, orsilver is processed on the surface of stainless steel can be used as thepositive electrode current collector. The current collector may haveminute irregularities on its surface in order to increase the adhesivestrength of positive electrode active materials, but may have a varietyof forms, such as a film, a sheet, foil, a net, porous materials,foaming materials, and non-woven reticulum.

A binder for the positive electrode active materials is a componentassisting the bond of active materials and a conduction agent and thebond for the current collector. In general, the binder is used in anamount of 1 to 50 wt % based on the total amount of a positive electrodemixture included the binder. High molecular polyacrylonitrile-acryliccopolymers can be used as the binder, but not limited thereto. Anotherexample of the hinder can include polyvinyllidene fluoride, polyvinylalcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose,regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethyl,polyethylene, polypropylene, ethylene-propylene-diene polymer termini(EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, and avariety of copolymers.

Other conduction agent and filler are the same as that described abovein relation to the negative electrode.

The separation film is interposed between the positive electrode and thenegative electrode. An insulating thin film having a high ionpermeability and high mechanical strength is used as the separationfilm. In general, the separation film has a pore diameter of 0.01 to 10μm and a thickness of 5 to 300 μm. For example, olefine-based polymers,such as chemical-resistant and hydrophobic polypropylene, a sheet ornon-woven fabric made of glass fiber or polyethylene, or the like can beused as the separation film.

The secondary battery of the present invention can be fabricated byincluding an electrode assembly in which the positive electrode and thenegative electrode, together with the separation film, are alternatelylaminated in an exterior casing, such as a battery casing, using anelectrolyte and then sealing the result. A typical method can beunlimitedly used as a method of fabricating the secondary battery.

Hereinafter, embodiments of the present invention are described indetail below. The following embodiments are intended to helpunderstanding of the present invention, and it should be noted that thefollowing embodiments me not intended to limit the scope of the presentinvention.

Embodiment 1

(Fabrication of Negative Electrode)

Conductive carbon was put in a composition in which graphite and abinder were mixed, and the composition was dispersed in water, therebyfabricating a slurry (where graphite:binder (SBR):conductive carbon(Super-P)=98.6:1:0.4 wt %). The slurry was coated on copper foil,sufficiently dried at a temperature of 130° C., and then pressed,thereby fabricating the negative electrode. The negative electrode had athickness of about 135 μm.

(Fabrication of Positive Electrode)

A slurry was fabricated through dispersion in NMP (where LiCoO₂:carbonblack:PVdF=95:2.5:2.5 wt %). The shirty was coated on aluminum foil,sufficiently dried at a temperature of 130° C., and then pressed,thereby fabricating the positive electrode. The positive electrode had athickness of about 140 μm.

(Fabrication of Battery)

A polypropylene separation film was laminated between the positiveelectrode and the negative electrode and received in the battery casing.Next, an electrolyte (where ethylenecarbonate(EC):fluoroethylenecarbonate (FEC) 90:10 wt %) was injected into thebattery casing and the battery casing was then sealed, thereby finallyfabricating the battery.

Embodiment 2

(Fabrication of Negative Electrode and Positive Electrode)

The same as the embodiment 1.

(Fabrication of Battery)

A polypropylene separation film was laminated between the positiveelectrode and the negative electrode and received in the battery casing.Next, an electrolyte (where ethylenecarbonate(EC):fluoroethylenecarbonate (FEC)=85:15 wt %) was injected into thebattery casing and the battery casing was then sealed, thereby finallyfabricating the battery.

Embodiment 3

(Fabrication of Negative Electrode)

Conductive carbon was put in a composition in which graphite and abinder were mixed, and the composition was dispersed in water, therebyfabric-sating a slurry (where graphite:binder (SBR):conductive carbon(Super-P)=95.6:4:0.4 wt %). The slurry was coated on copper foil,sufficiently dried at a temperature of 130° C., and then pressed,thereby fabricating the negative electrode. The negative electrode had athickness of about 135 μm.

(Fabrication of Positive Electrode and Battery)

The same as the embodiment 1.

Embodiment 4

(Fabrication of Negative Electrode and Positive Electrode)

The same as the embodiment 3.

(Fabrication of Battery)

A polypropylene separation film as laminated between the positiveelectrode and the negative electrode and received in the battery casing.Next, an electrolyte (where ethylenecarbonate(EC):fluoroethylenecarbonate (FEC)=85:15 wt %) was injected into thebattery casing and the battery casing was then sealed, thereby finallyfabricating the battery.

COMPARISON EXAMPLE 1

(Fabrication of Negative Electrode)

A slurry was fabricated by dispersing graphite:binder(SBR)=97:3.0 wt %in water. The slurry was coated on copper foil, sufficiently dried at atemperature of 130° C., and then pressed, thereby fabricating thenegative electrode. The negative electrode had a thickness of about 135μm.

(Fabrication of Positive Electrode)

A slurry was fabricated by dispersing LiCoO₂:carbonblack:PVdF=95:2.5:2.5 wt % in the NMP. The slurry was coated on copperfoil, sufficiently dried at a temperature of 130° C., and then pressed,thereby fabricating the positive electrode. The positive electrode had athickness of about 140 μm.

(Fabrication of Battery)

A polypropylene separation film was laminated between the positiveelectrode and the negative electrode and received in the battery casing.Next, an ethylenecarbonate (EC) electrolyte was injected into thebattery casing and the battery casing was then sealed, thereby finallyfabricating the battery.

COMPARISON EXAMPLE 2

(Fabrication of Negative Electrode)

A slurry was fabricated by dispersing graphite:binder(SBR):conductivecarbon (Super-F)=98.6:1:0.4 wt % in water. The slurry was coated oncopper foil, sufficiently dried at a temperature of 130° C., and thenpressed, thereby fabricating the negative electrode. The negativeelectrode had a thin of about 135 μm.

(Fabrication of Positive Electrode)

The same as the comparison example 1.

(Fabrication of Battery)

A polypropylene separation film was laminated between the positiveelectrode and the negative electrode and received in the battery casing.Next, an electrolyte (where ethylenecarbonate(EC):fluoroethylenecarbonate (FEC)=80:20) was injected into the batterycasing and the battery casing was then sealed, thereby finallyfabricating the battery.

COMPARISON EXAMPLE 3

(Fabrication of Negative Electrode)

A slurry was fabricated by dispersing graphite:binder(SBR):conductivecarbon (Super-P)=99.6:7:0.4 wt % in water. The slurry was coated oncopper foil, sufficiently dried at a temperature of 130° C., and thenpressed, thereby fabricating the negative electrode. The negativeelectrode had a thickness of about 135 μm.

(Fabrication of Positive Electrode)

The same as the comparison example 1.

(Fabrication of Battery)

A polypropylene separation film was laminated between the positiveelectrode and the negative electrode and received in the battery casing.An electrolyte (where ethylenecarbonate (EC):fluoroethylenecarbonate(FEC)=90:10 wt %) was injected into the battery casing and the batterycasing was then sealed, thereby finally fabricating the battery.

COMPARISON EXAMPLE 4

(Fabrication of Negative Electrode)

A slurry was fabricated by dispersing graphite:binder(SBR):conductivecarbon (Super-P)=92.6:7:0.4 wt % in water. The slurry was coated oncopper foil, sufficiently dried at a temperature of 130° C., and thenpressed, thereby fabricating the negative electrode. The negativeelectrode had a thickness of about 135 μm.

(Fabrication of Positive Electrode and Battery)

The same as the comparison example 3.

The negative electrodes of the embodiment and the comparison examplesand the compositions of the electrolytes are listed in Table 1 below.

TABLE 1 Negative electrode Conductive Electrolyte Graphite Binder (SBR)carbon EC FEC Embodiment 1 98.6 1 0.4 90 10 Embodiment 2 98.6 1 0.4 8515 Embodiment 3 95.6 4 0.4 90 10 Embodiment 4 95.6 4 0.4 85 15Comparison 97 3 0 100 0 example 1 Comparison 98.6 1 0.4 80 20 example 2Comparison 99.6 0 0.4 90 10 example 3 Comparison 92.6 7 0.4 90 10example 4 (Unit: wt %)

Charging and discharging experiments were performed on the batteriesaccording to the comparison examples and the embodiments, fabricatedusing the respective compositions. In order to increase the accuracy ofthe experiments, the batteries of the embodiments were fabricated forevery pair using the same method, and the same experiment was repeated.Conditions for the charging and discharging experiments are as follows,and the results of the experiments are listed in FIG. 1 and Table 2.

Conditions for the charging and discharging experiments

Charging: CC/CV mode, 13 C/4.2 V, and end current 50 mA

Discharging: CC mode and 1.0 C/3.0 V cut-off

TABLE 2 Charging Charging Capacity Charging Capacity % Capacity % % TestAt 30 min At 40 min At 1 hr Embodiment 1 3.0~4.2 V, 65.0 81.6 94.2Embodiment 2 1.3 C 65.1 81.6 94.2 Embodiment 3 65.2 80.1 93.1 Embodiment4 65.2 80.0 92.9 Comparison example 1 62.0 76.0 88.0 Comparison example2 63.0 76.9 89.2 Comparison example 3 58.5 71.3 80.4 Comparison example4 61.4 75.6 86.2 (Unit: wt %)

As shown in Table 2, the batteries of the embodiments have a highercharging ratio per unit time than those of the comparison examples. Asshown in FIG. 1, the batteries of the embodiments had an excellent cyclecharacteristic as compared with the comparison examples.

The batteries of the present invention are advantageous in that theyhave a high efficiency charging lifespan characteristic and enable highcapacity charging in a short time.

While the invention has been shown and described with respect to thesome exemplary embodiments, it will be understood by those skilled inthe art that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention as defined in thefollowing claims.

What is claimed is:
 1. A lithium secondary battery including a positiveelectrode, a negative electrode, and a non-aqueous electrolyte solution,wherein the negative electrode comprises a negative electrodecomposition including a negative electrode active material, awater-dispersible binder and a conduction agent, the water-dispersiblebinder is included in an amount of 1 wt % to 4 wt % based on a totalamount of the negative electrode composition iimd Inc conduction agentis included in an amount of 0.2 wt % to 08 wt % based on a total amountof the negative electrode composition, wherein the non-aqueouselectrolyte solution comprises 10 wt % to 15 wt % offluoroethylenecarbonate (FEC) based on a total amount of the non-aqueouselectrolyte solution and 85 wt % to 90 wt % of ethylenecarbonate (EC)based on a total amount of the non-aqueous electrolyte solution, whereinthe conduction agent is one or more selected from acetylene black,carbon black, and graphite, and wherein the water-dispersible binder isone or more selected from styrene-butadiene rubber,acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber,carboxymethyl cellulose, and hydroxypropylmethyl cellulose.
 2. Thelithium secondary battery of claim 1, wherein thefluoroethylenecarbonate (FEC) is included in an amount of 10 wt % to 15wt % based on a total amount of the non-aqueous electrolyte solutionincluding the flmiroethylenecarbonate (FEC).
 3. The lithium secondarybattery of claim 2, wherein ethylenecarbonate (EC) is included in anamount of 85 wt % to 90 wt % based on a total amount of the non-aqueouselectrolyte solution including the ethylenecarbonate (EC).
 4. Thelithium secondary battery of claim 1, wherein the conduction agent isone or a combination of two or more selected from acetylene black,carbon black, and graphite.
 5. The lithium secondary battery of claim 1,wherein the conduction agent is included in an amount of 0.2 wt % to 0.8wt %.
 6. The lithium secondary battery of claim 1, wherein thewater-dispersible binder is one or a combination of two or more selectedfrom styrene-butadiene rubber, acrylonitrile-butadiene rubber,acrylonitrile-butadiene-styrene rubber, carboxymethyl cellulose, andhydroxypropylmethyl cellulose.
 7. The lithium secondary battery of claim1, wherein the water-dispersible binder is included in an amount of 1 wt% to 4 wt % based on a total weight of an electrode composition.
 8. Thelithium secondary battery of claim 1, wherein the negative electrodeactive material has a particle diameter of 5 to 30 μm.